ADC PYQ UNIT 2
1. Discuss the generation of FM wave using direct method
2. Discuss the detection of FM wave using zero crossing detector
3. An FM wave with modulation index β = 1 is transmitted through an ideal
band pass filter with mid band frequency fc and bandwidth is 5fm, where
fc is the carrier frequency and fm is the frequency of the sinusoidal
modulating wave. Determine the amplitude spectrum of the filter output
4. Explain the concept of pre emphasis and de-emphasis.
5. Discuss the process of Detection of FM Waves by Phase locked loop
6. An angle modulated signal is given by s(t) = 100 cos [2πfct + 4
Sin2000πt]. Where, fc = 10 MHz, Find the peak frequency deviation. Is
this an FM wave or PM wave.
7. For an FM modulator with a modulating signal m(t)= Vm sin(300×103 t),
the carrier Signal Vc(t)=8 sin(6.5×106 t) and the modulation index = 2.
Find out the significant side band frequencies and their amplitudes
8. How PLL is used to detect the FM signal?
9. Explain the detection of FM wave using balanced frequency
discrimination
10.State and explain the concept of transmission bandwidth.
11.Draw and explain how PLL is used in detection of FM signal
12.What is the purpose of pre-emphasis and de-emphasis filtering? Explain
the filtering process with suitable sketches.
13.Draw the spectrum of FM wave and compare narrow band and wide
band FM
14.A carrier which attains a peak voltage of 5 volts has a frequency of 100
MHz. This carrier is frequency modulated by a sinusoidal waveform of
frequency 2 kHz to such extent that the frequency deviation from the
carrier frequency is 75 kHz. The modulated waveform passes through
zero and is increasing at time t=0. Write an expression for the modulated
carrier waveform
15.Why pre-emphasis and de-emphasis needed in FM? How to generate it?
16.A carrier of frequency 106 Hz and amplitude 3 volts is frequency –
modulated by a sinusoidal modulating waveform of frequency 500 Hz
and of peak amplitude 1 volt. As a consequence, the frequency deviation
is 1 kHz. The level of modulating waveform is changed to 2 volts peak
and the modulating frequency is changed to 2 kHz. Write the expression
for the new modulated waveform.
17.Compare and contrast NBFM with WBFM
18.Discuss the need of pre emphasis and de emphasis in FM and explain
their operations.
19.What are the two methods of producing an FM wave? And explain.
20.An angle modulated signal has the form v(t)=100cos(2πfct+4sin2000πt)
when fc=10MHz i) Determine average transmitted power ii) Determine
peak phase deviation iii) Determine the peak frequency deviation iv) Is
this an FM or a PM signal? Explain.
21.Derive the expression for FM signal from fundamentals and differentiate
narrow band FM and wide band FM.
22.For an FM modulator with a modulating signal m(t)= Vmsin(300×103 t),
the carrier Signal VC(t)=8 sin(6.5×106 t) and the modulator index = 2.
Find out the significant sideband frequencies and their amplitudes
23.Compare noise performance of PM and FM system
24.Explain the indirect method of generation of FM wave and any one
method of demodulating an FM wave
25.Discuss the generation of FM wave using direct method
26. Explain how FM signal is detected with the help of PLLs
27.Explain the detection of FM wave using balanced frequency
discrimination
28.Compare of FM and AM.
29.
